There have been increasing concerns about the significant decline in teenagers’ intentions to pursue STEM subjects or careers. This study examined how students’ perceptions of parental expectations, STEM cultural capital, mathematics/science self-efficacy, gender, and parents’ jobs were associated with STEM career aspirations and tested whether these associations differed by school level. Data were collected from 1,864 junior and 665 senior secondary students in Hong Kong via an online survey. Results indicated that, perceived parental long-term expectations were closely linked to STEM career aspirations, whereas, perceived parental short-term expectations were closely linked to self-efficacy. Out-of-school STEM experiences and STEM media consumption both had positive impacts on aspirations and shaped different aspects of students’ perceived parental expectations. Additionally, significant gender differences were found in STEM media consumption, self-efficacy, and aspirations. These relationships mainly were invariant across school levels. However, the indirect paths from STEM media consumption to aspirations via self-efficacy varied significantly between junior and senior secondary students. Based on these findings, this study argues for the essential role of perceived parental expectations in shaping STEM career aspirations for teenagers. STEM cultural capital may be more productive and supportive if it promotes teenagers’ interpretations of parental expectations and their mathematics and science self-efficacy. Copyright © 2022 Informa UK Limited, trading as Taylor & Francis Group.